No they don't.

While there is indeed a turning area at the end (enlarged recently), the video in post #70 clearly shows another Pegasus B738 performing a 180 on the runway itself (to save time?).

Agreed, there is no need to use the pad. Most operators in Turkey use the runway, saves time and stops half the pax from standing up after touchdown! Unlikely, the turn would be to the right then left, which would put the aircraft the other way round. Also there is a about 10 metres plus of land between the runway edge and the escarpment at Trabzon, hence if the nose wheel went on the mud, they would just stop. Turkish TV records passengers saying aircraft was sliding and twisting before a loud crash and rapid nose down attitude.

I agree. Appears to be an orange flash at the 19sec mark on that video.
Hard to say what, but an engine surge/stall is definitely a candidate.
Nasty dark wet night too, no doubt slippy runway.

First Officer is pf, weather is at minimums. They are expecting to see the runway at minimums. At minimums they see the runway and the first officer disangages the autopilot but at the same time he presses the toga buttons. Captain takes over and lowers the nose and retards both thrust levers to idle, they land at idle thrust and aircraft was dispatched with one reverser inop. The captain deploys the thrust reverser of the left engine and releases the right engine. Since he hadn't disconnect the auto throttle right engine goes to TOGA thrust. Aircraft starts to accelerate and skids off the runway from the left. Right engine saparates. All passengers evacuate the aircraft from the rear door. No smoke in the cabin no injuries.

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Lots of runway behind the aircraft.

Have a look at the video at post #70, the initial turn is to the left and then back hard towards the right.

No, have a look at the video in post #70, they perform a left swing followed by right backtrack, in almost exactly the same place as the accident.

I have seen bird strikes get caught up in the nose steering cables on 737’s before

Remember the KLM runway excursion in BCN due nose wheel steering malfunction.

I know bats are not strictly birds, but hey, they are nocturnal aviators.

Shearwaters fly at night, noisily congregating on cliff areas, but that's in the breeding season which I don't think is now.

They do migrate through Turkey but slightly later than this.

It’s about 5% at MLW with 26k engine.

Just because this PGS does this, it doesn't mean its a procedure.Most aircraft making a normal touchdown can vacate at the second taxi way without backtrack. (plenty of you tube vids on this ) some make a move to parallel the centre line to the left before turning right, but its nothing like a sharp turn. We will know more tomorrow ;)

And your source is?

Someone in that company....

The word on the ground is an uncommanded thrust increase on engine 2 which took them off the runway

Also heard there are five recent occurences of the the same

I suppose it depends on your definition of "sharp turn". It looks like a standard 30° RET for traffic landing on 29, which makes it a 150° turn if you're coming from the 11 end.

But either way that's irrelevant, the debate was whether the incident was a 180 that went wrong, and your assertion that

I'd suggest that, unless Pegasus is one of the few airlines that has paid Boeing the hefty premium to have the optional tiller on the RHS of the 737NG, a 180 will be in whichever direction the Captain decides to execute it.

Though if it was a runaway engine, it's all pretty academic.

The turning issue is a bit of a red herring TBH, as observed, the Captain will decide according to his/her wishes. I am curious to understand how a 737NG can still have TOGA auto throttle more than 2 secs after ground air switch senses touchdown or with a TRA split of more than 10 degrees? This theory would mean they landed with the A/T armed and then somehow pressed TOGA before 2 secs and then selected asymmetric reverse? seems like far too may swiss cheese holes! Regarding info from "someone on the ground" having been based in Trabzon for 6 months I would take that with a very large pinch of salt..
Of course being Turkey its possible the Captain lit a cigarette and dropped it, lent forward to catch it and opened the T/L, after the Correndon fire at AYT due smoking we wouldn't be surprised!

Dongle..Can you provide refs for the uncommanded asymmetric TL movements please

From an Indian news site:

The pilot, co-pilot and crew have now made statements to Trabzon prosecutors and both pilots passed breathalyzer tests, the Dogan news agency said.

"When we were going to make our usual manoeuvre towards the right from the seaside by reducing our speed, the right engine suddenly gained speed for a reason we do not know," the pilot was quoted as telling the prosecutors.

"Due to this speed, the plane got out of our control and suddenly swung to the left and got stuck into the mud in the cliff."

www.ndtv.com

During landing phase, the aircraft systems receive an "on the ground" information from the Flt/Gnd switches, spoilers are deployed, left engine reverse thrust applied. If in this situation the A/T can command TO/GA thrust on a single engine, I would say that this a serious design flaw.

As far as I know, if the aircraft has been dispatched with the right reverse inop, the reverse mechanism will be locked by the technical staff and if the pilot activates the reverse thrust levers only the left engine would go to reverse mode. Would a pilot in such a situation pull only the left reverse lever or both (instinctively)? Or is there a defined procedure which prohibits the pilots to activate an inoperative reverse thrust lever during landing?

Why I am asking this?

Let's say that the captain as taken over the controls and landed the aircraft safely. If he would activate both reversers the autothrottle would not be able to advance the right thrust lever to TO/GA thrust position because the pilots right hand pulls the levers back. Only after cancelling the reverse thrust the captain can remove his right hand from the throttle. By this time the aircraft must have decelerated to 60 kts. Let's say the right engine goes to TO/GA mode at this point. It would take a couple of seconds for the full thrust to developed. During this time the pilots should have noticed this problem and retarded the thrust levers (in my opinion).

Aquaplaning marks aren’t easy to see.
 

I searched in google aquaplaning marks on runways and believe me from the pictures I saw isn’t easy to see them unless a good closeup picture is taken; which make sense because aquaplaning is the fenomena when the tires detach from the runway for a x time. I think from this pictures is difficult to see them. Less wait for a closer picture of the runway.